The present invention is in the field of electronic circuits and camera systems. More particularly, the present invention is directed to a system for surveillance using digital images and image servers.
Many types of camera surveillance systems are known. Typical building surveillance systems today capture analog video signals from one or more video cameras and transmit those signals to a security panel for viewing by security personnel. Deployment of such systems over a large area and making the video images available over a network can be problematic because of the large bandwidth requirements of the video signal. Monitoring of multiple analog cameras is also difficult; for example, a human viewer's attention may not be on the security panel or directed to the correct camera image at the time an incident occurs. An, in general, the number of cameras a human can effectively monitor is limited. While techniques for motion detection in surveillance systems are known, the complexity and expense of incorporating these techniques into analog systems has limited the use of motion detection in many video surveillance systems.
Another problem that arises in analog surveillance systems is storage and playback technology of analog video data. Typical security cameras, at a retail store for example, employ videotape technology wherein full-motion video is continuously recorded, without regard to whether an incident of interest has occurred. Video tapes are retrieved and played back on the rare occasions when an incident occurs. A major problem with such systems is that the videotapes are often recorded at the slowest speed, giving the poorest image quality, and are repeatedly rerecorded. As a result, playback image quality is often very poor and when an incident does occur, investigators cannot get a clear enough image of individuals involved in the incident to make an identification. In response to this problem, the Federal Bureau of Investigation has established a laboratory program whose primary function is to help law enforcement personnel enhance poor quality images from video surveillance systems in order to aid in investigations.
It is known to make digitized video images available over the web for presentation by a web browser. Generally, such systems periodically update a full-frame captured still image from a camera using a push (controlled at the server side) or a pull (controlled at the client side) technology. Such systems have had a limited deployment to make images of such things as ski slope weather conditions, elephant houses at a zoo, or children at a day care center, available over the web using a standard web browser. In some applications, such as the day care center, access to the image is password protected so that only authorized viewers can receive the images.
One group of cameras and camera servers for these applications are marketed under the brand name Axis. However, these installations are generally limited to single or a few cameras and do not have the ability to be deployed as a flexible and fully functional surveillance systems. Standard Axis technology also generally relies on full-frame updating and has only limited ability to reduce bandwidth of images.
A number of techniques are known for compressing digital video information. Well known techniques for digital video include hardware assisted techniques such as MPEG, DVL Motion JPEG, and software-only techniques such as QuickTime, Video for Windows, RealVideo, or AVI. Some of these techniques include mechanisms for processing and transmitting delta frame information, wherein delta frames encode information about pixels that have changed between one frame and another. However, these compression techniques for the most part are concerned with the quality of reproduction of real-time video image and have not been optimized for use in surveillance systems or for use in systems that do not contain custom video playback software or hardware.
What is needed is a flexible surveillance system that can capture image data from a number of digital cameras and make that data available to viewers in a variety of different ways. In some applications, what is further needed, is a surveillance system with a basic architecture that is scalable, allowing for efficient installation, coordination, and control of one, to a few, to thousands of individual cameras and one to a few to thousands of individual clients. Additionally, what is needed is an integrated system for digital surveillance that at every step of image processing optimizes images for easy storage, analysis, transmission, and presentation in a surveillance system.